RU2025016C1 - Method of correction of compensation tuning under mode of fault to ground - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: conventional system of adjustment of tuning acts under condition of fault without saturation of reactor. With saturation of reactor its current exceeds set value and threshold elements begin operate successively depending on magnitude of signal proportional to difference of currents under saturated and unsaturated states within half-period of change of instantaneous value of current of reactor. They connect or disconnect corresponding capacitors depending on magnitude of signal which provides for acute tuning with saturation of reactor. EFFECT: provision for acute tuning of compensation. 1 dwg

Description

 The invention relates to electrical engineering and can be used in electric networks 6-35 kV operating in compensated neutral mode.

 Known methods for tuning arc suppression reactors based on measuring the frequency of free oscillations of the neutral voltage that occur after the extinction of the arc in the mode of alternating burning, or measuring the phase of the neutral voltage relative to the voltage of the damaged phase with a stable circuit.

 A device is also known for automatic tuning of an extinguishing reactor, where one of the controlled parameters, according to the measurement results of which the reactor inductance is controlled, is its current.

 However, this regulation principle is not applicable for an intermittent arc, when the channel for measuring reactor parameters is blocked and there is a period for regulation with the help of the reactor tuning unit for an intermittent arc using parameters from a voltage measuring transformer.

 The disadvantage of this device is the need to select control logic in the ground fault mode and the associated insufficient speed, for example, during short-term saturation of arc suppression reactors, when due to the presence of a free component of the magnetic flux at the time of the next arc ignition, the setting is shifted to the overcompensation region. Saturation of reactors can also occur as a result of the appearance on the neutral voltage increased relative to the nominal values (Likhachev F.A. Earth faults in networks with isolated neutral and compensation of capacitive currents.- M .: Energy, 1971, pp. 107-108). Disturbances associated with saturation can lead to a significant increase in current at the site of damage during stable arc burning and to a significant increase in overvoltages with the alternating nature of arc burning. Moreover, the required setup time in these cases is desirable to have as little as possible. So, dangerous overvoltages can occur already after 0.02 s after the next extinction of the arc, i.e. for the time required for known devices only to identify the nature of arc burning and the transition from one control logic to another.

 The aim of the invention is to increase the speed of elimination of the mismatch of compensation associated with the saturation of the arcing reactor.

 The goal is achieved by the fact that in the earth fault mode, the current parameter of the arcing reactor is measured and the compensation current is changed depending on this parameter. As the current parameter, the instantaneous value of the reactor current is used, which is compared with a setting proportional to the amplitude value of the reactor current in an unsaturated state, and in case of excess of the current over the setting, the compensation current is proportional to the comparison result.

 The proposed method differs from the known ones by introducing into the known controller an additional control channel for the current of the extinguishing reactor, which provides high-speed control of the compensation setting both in the intermittent mode and in the steady-state mode of arc burning.

 The increase in performance is explained by the fact that as a control parameter, a value that directly determines the detuning is used - the compensation current, and not the inertia measured degree of compensation detuning.

 The drawing shows a diagram of a device that implements the proposed method.

 The extinguishing reactor 1 with a standard tuning control system is additionally equipped with a capacitor box 2, the semiconductor switches of which are controlled by a block 6 of individual threshold elements 6.1-6.3. A signal proportional to the reactor current is fed to a half-wave rectifier 3, the output of which is fed to the measuring device 4. At the second input of the measuring device in an unsaturated state, a signal is supplied to the block 6 of threshold elements through a diode 5. The measuring device is an adder, the output of which is the difference between the instantaneous values of the current reactor current and the amplitude of the unsaturated reactor current, set in the form of a set point. The signal at the input of block 6 is equal to the excess of the instantaneous value of the reactor current above the setpoint. The prefix capacitors are selected equal in power, their number is determined by the required discreteness, and the power is determined by the depth of correction of the compensation current. Capacitor switches are controlled by individual threshold blocks. The response level of the threshold blocks increases with the same discreteness as the power of the capacitors.

 In the normal mode and in the mode of closure without saturation of the reactor, the usual adjustment control system operates, since the signal proportional to the degree of saturation of the reactor from the output of device 4 is less than or equal to zero. When the reactor is saturated, its current exceeds the setpoint of device 4 and a signal proportional to the difference in currents in saturated and unsaturated states enters through the diode 5 the input of threshold elements. As the instantaneous value of the reactor current inside the half-cycle increases, the threshold elements 6.1, 6.2, 6.3, ... begin to act sequentially, connecting capacitors C1, C2, C3, respectively ... As the instantaneous value of the saturated current decreases inside the half-cycle, commands are formed to turn off the capacitors in in reverse order ... C3, C2, C1. It should be noted that despite the formation of a command to turn off the capacitors, the switch remains in a conductive state until the current in it passes through zero. Thus, at each half-cycle, an additional capacitance is connected to the circuit of the zero sequence, which ensures sharp tuning during saturation of the reactors.

 If there is no saturation, the difference between the currents of the unsaturated and saturated reactor at the output of the device 4 is less than or equal to zero, and the compensation device 1 operates on a signal from a standard control system. When saturated, the signal from the output of the device 4, which is proportional to the excess of the reactor current over its unsaturated value, is supplied to the compensation adjustment control channel. The effect of the proposed correction on the compensation adjustment process ceases as soon as the reactor current becomes less than the setting proportional to the current of the unsaturated reactor.

 Such a comparison device can be made on the basis of standard automation elements.

 The proposed method is characterized by ease of implementation and high speed elimination of the mismatch of compensation caused by saturation of the arcing reactor. This helps to prevent dangerous overvoltages and limit the destructive effect of the electric arc during saturation of the arcing reactor, which increases the reliability of power supply.

Claims (1)

 METHOD FOR COMPENSATION ADJUSTMENT METHOD IN EARTH CLOSING MODE, which consists in measuring the current parameter of the arcing reactor and changing the compensation current depending on this parameter, characterized in that, in order to improve the speed of eliminating the compensation detuning associated with saturation of the arcing reactor as the current parameter, the instantaneous value of the reactor current is used, which is compared with a setting proportional to the amplitude value of the reactor current in the unsaturated state, and in the case of A rise in current above the setpoint changes the compensation current in proportion to the result of the comparison.

Images